1. Field of the Invention
This invention relates to polymer concrete compositions and methods for repairing or resurfacing concrete surfaces, such as, roads, bridges, decks, runways, etc., and, more particularly, is directed to slump-resistant, curable polymer concrete compositions suitable for rolling onto a concrete surface to resurface it and to methods for applying a polymer concrete surface to concrete surfaces of roadways, runways, sidewalks, floorings, roof decks, water tanks, reservoirs, swimming pools, retaining ponds, dams, median barriers, bridges, buildings and other concrete structures.
2. Prior Art
The sealing of deteriorated concrete or asphalt-concrete or latex-concrete road surfaces, pavements, bridge decks, malls, garage decks, airport runways and ramps, etc., and the provision of a new durable wear surface; cannot be readily accomplished through the use of conventional paving materials such as concrete, latex-concrete or asphaltic-concrete. Various synthetic resin systems have been evaluated as sealers and as binders for wear courses in attempting to resolve this problem. Epoxy resins, acrylic resins, urethanes and modified urethanes and unsaturated polyester resins have been investigated under a variety of conditions with limited success.
Work on developing suitable polymer concrete type material for paving roads and bridges has been continuing for over 25 years. A paper by N. S. Estrada entitled "Paving of Roads and Bridges With Unsaturated Polyesters" (Section 20-F, pages 1-10) was presented before the 25th Annual Technical Conference, Reinforced Plastics/Composites Division of The Society of Plastics Industry, Inc. in 1970 and dealt with a review of work done and the shortcomings of the approach used. This work covered "broadcasting" sand over liquid resin applied to highways and bridges. Illustrative prior art polymer concrete compositions are also described in U.S. Pat. Nos. 3,575,785; 4,375,489 and 4,400,413 and the references cited therein. They comprise a resin or polymer, e.g., a vinyl ester resin (U.S. Pat. No. 4,375,489) or an acrylate resin (U.S. Pat. No. 4,400,413), an inert particulate material, e.g., sand or aggregate, and a curing agent.
A limiting characteristic of the prior art systems is the tendency of the polymers or resins or components thereof, e.g., unsaturated polyester and unsaturated monomer such as styrene, to run off the surface being coated, to run downgrade on a sloped surface, and/or to separate from the aggregate, e.g., sand, which is a necessary component of polymer concrete compositions. Because of their loose, runny characteristics, the prior art polymer concrete materials cannot be trucked and must be prepared on-site, i.e., the lane adjacent to the lane being resurfaced must be used for the mixing and metering equipment and supply vehicles which are on the move to keep up with the paver. As a consequence, for each lane being resurfaced, two lanes are taken out of service, the one being resurfaced and the one next to it. In order to resurface one lane of a two-lane highway with polymer concrete, the entire highway would have to be taken out of service, which in the usual case in unacceptable. In resurfacing a single lane of a busy multiple lane highway, the loss of two lanes for even short periods results in traffic tie-ups and consequent hazardous conditions. Also, it has been estimated that 25% of the cost of highway work is devoted solely to traffic control devices and procedures, so that the less traffic that needs to be diverted, the lower will be the cost of the resurfacing job. The polymer concrete compositions of this invention, on the other hand, can be prepared in a convenient off-site location and trucked with essentially no leakage to the lane being repaired, avoiding the need to take any additional lanes out of service, and, thus, closely resemble the systems currently used to lay down asphalt wherein only the lane being resurfaced need be closed to traffic.
Attempts to adjust the rheology of the prior art systems, for example, by adding a material that increases the viscosity and thereby retards or eliminates run-off or separation are not successful. U.S. Pat. No. 4,400,413 (Col. 6, lines 55-58) teaches the addition of thickening or rheological control agents. But, the addition of such agents to the polymer concrete composition presents the additional problem of making extremely difficult, or preventing, the uniform distribution of the components throughout the polymer concrete composition and/or the adequate wetting out of the aggregate with the curable polymer or resin essential for bonding the aggregate together and to the surface being repaired. If the viscosity increasing agent is added to the polymer-catalyst mix, before mixing with aggregate, it is extremely difficult, if not impossible, because of the resulting increase in viscosity, to suitably wet-out the aggregate. Prolonged mixing is ruled out if the system is active because of the presence of the curing catalyst. If the curing catalyst is added last, the increased viscosity of the system caused by the presence of the viscosity increasing agent prevents uniform distribution of the catalyst and results in an uneven cure such that those portions of the composition containing little or no catalyst cure too slowly or not at all and those portions containing too much catalyst cure prematurely. Non-uniform distribution of the components of the polymer concrete composition renders it extremely difficult or impossible to control the timing of the steps in preparing the mix and applying it to the surface being repaired and obviously results in a coating having non-uniform physical strength properties which is unacceptable from a structural standpoint.
It is well known in the sheet molding compound (SMC) prior art and the bulk molding compound (BMC) prior art to provide molding compounds having time-delayed thickening action by the use of Group IIA metal oxides or hydroxides or polyisocyanates. However, none of these compositions are suitable for use as slump-resistant, curable polymer concrete composition suitable for coating or rolling onto a concrete surface to resurface same and none of previously known SMC or BMC compositions contain aggregate, e.g., crushed stone, gravel or sand, which is necessary for providing the strength, traction, wearability and weatherability required for resurfaced concrete surfaces.
None of the prior art identified above and no prior art is known which teaches the use of a delayed thickening system such that the components of a polymer concrete composition containing aggregate can be readily and uniformly mixed and the aggregate can be wetted out by the curable polymer at relatively low viscosities yet thicken at a predetermined time after or during application to a concrete surface to provide a low or no slump, low odor system which can be easily worked and shaped, such as by troweling, spreading, rolling,, etc., and which does not result in the curable polymer running off the surface being repaired, running downgrade on a sloped surface, or separating from the aggregate.